The present invention relates to microtome knife holders and more particularly to improvements in the versatility of such holders, the accessibility of replaceable knives and the inter-changeability of holders for different types of knives.
One advantage of the present invention is provided by a dove-tailed rail secured to a holder base which is rotatable on an axis coincident with the cutting edge of a plurality of knives each held by a different type of holder. An individual holder to hold a disposable, Ralph, glass or replaceable knife is mounted by sliding the selected holder on to the dove-tailed rail and then clamping it in the desired position. Prior art devices required that the entire base and be replaced as taught by DE-P 34 13 278.3.
The invention also relates to a clamping device for the cutting knife of a microtome comprising a support element provided on the microtome and at least one clamping jaw adjustable along a guide means of the support element longitudinally of the cutting blade of the knife and arrestable on said supporting means.
A clamping device of this type is disclosed in DE-PS 36 16 659. The clamping jaws are guided in a longitudinal groove and the support element comprises at least one longitudinal slot through which a fastening means extends for securing the clamping jaws to the support element.
The invention is based on the object of improving a clamping device of the above-mentioned kind such that different clamping jaws can be easily and quickly combined with the support element, exchanged with each other in modular fashion and are reliably secured to the support element.
According to the invention, this object is solved in that the guide means is formed of a prism rail having a substantially dovetailed profile, a slotted foot portion of the clamping jaw formed with a matching complementary profile and compressible by means of at least one screw engaging around said prism rail.
A particularly stable clamping of the knife is accomplished if, in accordance with one embodiment of the invention, the cutting knife is clamped-in by means of two clamping jaws which are provided substantially symmetrical on both sides of the area of cut. It is also desireable that the space between the clamps be adjustable in order that maximum stability can be achieved. Depending on whether it is more important in the individual cutting operation to provide free accessibility of the area of cut or a high resistance to moment and a high resistance of the knife to bending in order to enable a smooth, vibration-free cutting operation, the distance between the points where the knife is clamped-in can be adjusted without problem in accordance with the requirements of the individual applications.
If it is desired to provide free accessibility to the cutting knife is as freely accessible as possible, according to another embodiment of the invention, the cutting knife is clamped-in by means of a single main clamping jaw which is disposed laterally of the area of cut. In order to provide greater stability without substantial loss of free accessibility to the cutting knife, the free end of the cutting knife clamped-in the main clamping jaw can in addition be clamped-in a supplementary clamping jaw which is smaller than the main clamping jaw and is easier to be secured.
In any case, the back of the cutting knife advantageously rests on a supporting rail which is vertically adjustable by means of adjustment screws to provide a clamping mechanism for the knife which can be easily adapted to different commercially available knives of different shapes and which allows the cutting blade of the knife to be adjusted to the pivot axis of the rotatable base.
According to the invention, an insertion of the knife from the front and a quick exchange and reliable clamping-in of a replaceable knife is enabled in that a clamping latch is pivotally mounted on the top end of the clamping jaw, which latch can be swung down to contact the side of the knife resting with its back on the supporting rail, said clamping latch being adapted to be pressed against the knife by means of a tensioning screw screwed through the clamping latch, the screw end being supported on a support surface of the clamping jaw.
The clamping means of the invention allows the cutting knife to be inserted from the front (a direction normal to the orienting surface) so that it no longer needs to be inserted from the top or side, which often results in damage being caused to the cutting blade.
According to the invention, the cutting knife is reliably retained in that a narrow edge of the clamping latch extending in parallel to the cutting edge rests on the cutting knife. Said edge is brought in backlash-free line contact with the knife surface and the knife is reliably pressed against its support surface in particular in that, in accordance with further preferable features of the invention, the edge resting on the cutting knife is provided on a floating member, pivotally mounted to the clamping latch and the edge includes a central recess in its longitudinal extension.
According to the invention, the tension screw is provided on the pivotal clamping latch and serves to tighten the exchangeable cutting knife with an automatic adaptation to different knife thicknesses so that the usual commercial cutting knives differing highly as regards thickness and cutting angle can be quickly and reliably clamped-in by a one-hand operation. To impart the full clamping force to the to turn the tension screw by approximately 180.degree.. Unlike in known knife holders, only one single control member is required in order to clamp-in the knife and to enable an adjustment to a specific knife thickness.
The floating member facilitates the adjustment to different cutting angles, reduces the surface pressure encountered at the point of contact with the knife and ensures a parallel alignment between the knife and the knife support. As a result, new and old knives can be used without restriction and the so-called "dragging cut" which occurs in case of non-parallel adjustment is eliminated.
According to a further advantageous feature of the invention, the clamping jaw is provided with a bevel to further facilitate the manipulation of the quick-action clamping means, said bevel surface being so located in the path travelled by the end of the tension screw when the clamping latch is swung towards the knife that, during the pivotal movement of the clamping latch, it axially displaces the screw end out of the area of the support surface cooperating with the screw end and releases it again at the end of the pivotal movement, a return spring biases the clamping latch against this axial movement.
In this way it is possible, by a mere axial displacement, to remove the clamping latch from the knife flank, i.e., to open the clamping latch, so that the knife can be exchanged or longitudinally shifted to expose another area of cut. By exerting a slight pressure on the tensioning screw, the clamping latch is then automatically closed again via the inclination of the bevel surface.
According to the invention, an exchange or shift of the cutting knife is further facilitated in that a spring is provided which holds the clamping latch in a position in which it is swung away from the knife which spring retains the clamping latch in its opened position after it has been unlocked. A configuration which is particularly easy to manufacture is provided in that a spring is provided on the axis of the clamping latch which tends to urge the clamping latch both in axial direction and to lift it away from the cutting knife in pivotal direction.
Finally, according to the invention, the abutment surface for the cutting knife includes in proximity to the cutting blade a prism guide of substantially dovetailed shape for a knife guard which is movable longitudinally. Appropriately, the guard is formed with the dovetailed profile corresponding to the recess and includes at its upper edge a lip projecting around the cutting blade to protect the cutting blade and, furthermore, to prevent the knife from inadvertently moving away from the knife orienting surface when the clamping latch assumes its opened position. Furthermore, a handle is provided in proximity to one end of the guard.
In this way, a guard is provided which is easy to manufacture and whose guide means is disposed fully below or flush with the knife support surface so that it does not impair in any way the insertion or exchange of the cutting knife and reliably protects the knife also against stronger outer influences and can be easily and quickly removed from the cutting edge at the beginning of the cutting operation. Furthermore, the guard prevents the cutting knife from moving away from its support surface when the clamping means assumes its opened position.
The clamping device of the invention is furthermore advantageous in that it can be easily disassembled so that the component parts can be disinfected individually in an easy fashion.